1. Technical Field
The present invention relates to an image formation apparatus, and more particularly relates to an image formation apparatus which exposes light onto a photosensitive body and forms an electrostatic latent image.
2. Related Art
In an electrophotography-type image formation apparatus, which exposes a photosensitive body surface to form a latent image, density variations within a page (within an image on the page) are caused by various factors. For example, variations in photosensitivity of the photosensitive body, charging variations, variations in exposure amounts, variations in distance between the photosensitive body and a developing sleeve, transfer variations and so forth can be mentioned as such factors.
Various techniques have been proposed as techniques for correcting the density irregularities caused by these factors.
For example, there are: (1) a technique of correcting density irregularities with image data; (2) a technique of pre-memorizing photosensitive body characteristics of a photosensitive body, comparing therewith photosensitive body characteristics subject to the effects of the passage of time, which is an amount of time of use of the photosensitive body, temperature and humidity of the vicinity of the photosensitive body, a number of sheets printed and the like, measuring density irregularities, and correcting one or more of charging quantities, exposure quantities, development quantities and transfer quantities; (3) a technique of correcting exposure amounts in accordance with an average value and variations of latent image potential over a full turn of a photosensitive body; and so forth.
A technique (4) of separately using exposure amounts that are required for controlling image density and exposure amounts that are for correcting page density irregularities has also been proposed.